Mechanistic understanding of molecular catalysts for water oxidation, carbon dioxide and proton reduction-important step in developing non-fossil fuels

Dnr:

SNIC 2017/5-43

Type:

SNAC Small

Principal Investigator:

Sascha Ott

Affiliation:

Uppsala universitet

Start Date:

2017-07-31

End Date:

2018-08-01

Primary Classification:

10404: Oorganisk kemi

Webpage:

http://www.kemi.uu.se/Research/principal-investigators/sascha-ott/

Allocation

Abstract

Mechanistic understanding of catalytic pathways is of prime importance for the development of functional catalysts. This project emphasizes on a) Electrocatalytic carbon dioxide reduction using Ruthenium catalysts b) Photo-induced catalytic water oxidation using Iron and Cobalt catalysts c) Proton reduction with low valent iron complexes. a) CO2 reduction serves as one of the renewable carbon-neutral sources to produce low-carbon products. CO is one of the components of water gas which is presently combined with gasification of coal to produce pure hydrogen. HCOOH is one of the most promising materials for hydrogen storage today since it readily decomposes into H2 and CO2 in the presence of a suitable catalyst. CH3OH has an advantage of being a liquid. Methane is more easily stored than hydrogen. Thus CO2 reduction can also be readily employed on commercial scale to meet the urgent requirements of alternative renewable sources of energy. Designing catalysts for CO2 reduction is still in its preliminary stage and is a blooming area of research. As stated above, to build efficient catalysts, the understanding of mechanistic details is very important and for that computational tools are essential. Some of the ruthenium complexes synthesized by our group have been studied recently and using DFT, we have been able to understand the fact that the first electron entering the ligand fortified the reduction of CO2 bound to the metal center. b) Solar water splitting process requires coupling of two half-reactions: (i) oxidation of H2O generating the reducing equivalents and (ii) reduction of protons to molecular hydrogen. As water oxidation is the bottle neck of this process, development of water oxidation catalysts (WOC) have been exhilarated. We want to use earth abundant, cheap first row transition metals which can sustain multiple redox levels. Fulfilling the above mentioned criteria, Iron and Cobalt complexes exemplify a prospective candidate. Although few iron and cobalt complexes have been reported to catalyze water oxidation , the complete mechanism is yet to be revealed. In this quest we have been investigating robust Fe and Co polypyridyl complexes. As the catalytic water oxidation results are very promising, detail mechanistic investigations are being commenced to proceed towards developing improved catalysts. Recently we have been able to understand strong influence of the chloride ion in the catalytic water oxidation activity and complete mechanism involving high valent metal oxo species is under investigation. c) Low-valent Fe compounds serving as models of the H2ase active sites have shown to be promising proton reduction catalysts. In the project we want to study transition states of the catalytic process. 1. BA. Johnson, S.Maji, H.Agarwala, TA White, E.Mijangos, and Sascha Ott Angew.Chem. 2016, 55, 1825–1829. 2. B.Das, A.Orthaber, Sascha Ott, and Anders Thapper accepted ChemSusChem